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initialize - Kokkos documentation

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initialize¶

Defined in header <Kokkos_Core.hpp>

Usage:

Kokkos::initialize(argc, argv);
Kokkos::initialize(Kokkos::InitializationSettings()  // (since 3.7)
                       .set_disable_warnings(true)
                       .set_num_threads(8)
                       .set_map_device_id_by("random"));

Initializes the Kokkos execution environment. This function must be called before any other Kokkos API functions or constructors. There are a small number of exceptions, such as Kokkos::is_initialized and Kokkos::is_finalized. Kokkos can be initialized at most once; subsequent calls are erroneous.

The function has two overloads. The first one takes the same two parameters as main() corresponding to the command line arguments passed to the program from the environment in which the program is run. Kokkos parses the arguments for the flags that it recognizes. Whenever a Kokkos flag is seen, it is removed from argv, and argc is decremented. The second one takes a Kokkos::InitializationSettings class object which allows for programmatic control of arguments. Kokkos::InitializationSettings is implicitly constructible from the Kokkos::InitArguments ^{deprecated in version 3.7}.

Interface¶

Kokkos::initialize(int& argc, char* argv[]);                 //             (1)
Kokkos::initialize(InitArguments const& arguments);          // (until 3.7) (2)
Kokkos::initialize(InitializationSettings const& settings);  // (since 3.7) (3)

Parameters¶

argc: Non-negative value, representing the number of command line arguments passed to the program.
argv: Pointer to the first element of an array of argc + 1 pointers, of which the last one is null and the previous, if any, point to null-terminated multibyte strings that represent the arguments passed to the program.
arguments: (deprecated since version 3.7) C-style struct object is converted to Kokkos::InitializationSettings for backward compatibility.
settings: class object that contains settings to control the initialization of Kokkos.

Requirements¶

Kokkos::finalize must be called after Kokkos::initialize.
Kokkos::initialize generally should be called after MPI_Init when Kokkos is initialized within an MPI context.
User-initiated Kokkos objects cannot be constructed until after Kokkos::initialize is called.
Kokkos::initialize may not be called after a call to Kokkos::finalize.

Semantics¶

After calling Kokkos::initialize, Kokkos::is_initialized() should return true.

Example¶

#include <Kokkos_Core.hpp>

int main(int argc, char* argv[]) {
    Kokkos::initialize(argc, argv);
    {  // scope to ensure that my_view destructor is called before Kokkos::finalize
        Kokkos::View<double*> my_view("my_view", 10);
    }  // scope of my_view ends here
    Kokkos::finalize();
}